6 def overlap(box, center, D):
  7     def check_in(point, hibound):
  8         return 0 <= point and point <= hibound
  9     def check_edge(center, D, bound):
 10         return check_in(center + D, bound) or check_in(center - D, bound)
 11     # check edges overlap
 12     overlap = check_edge(center[0], D, box[0]) and check_edge(center[1], D, box[1])
 13     xleft   = max(center[0] - D, 0)
 14     xright  = min(center[0] + D, box[0])
 15     ybottom = max(center[1] - D, 0)
 16     ytop    = min(center[1] + D, box[1])
 17     return (overlap, xright-xleft, ytop-ybottom)